/Engine/Plugins/Online/OnlineSubsystemUtils/Source/OnlineSubsystemUtils/Public/VoicePacketBuffer.h
Pop RequestedSamples of float samples into DestBuffer. Returns the number of "non-silent" samples copied into the buffer- the remainder of the buffer will be filled with silence. This should be called on the audio render thread.
int32 PopAudio ( float * DestBuffer, uint32 RequestedSamples )